Semiconductor memory device and method for manufacturing the same

Abstract

A semiconductor device includes a semiconductor substrate, first and second stack units disposed over the semiconductor substrate, and a feature disposed between the first and second stack units. Each of the first and second stack units includes at least one stack that includes a conductive film and a dielectric film stacked on each other. The feature includes a plurality of repeating units and a plurality of separators disposed to alternate with the repeating units. Each of the repeating units includes an inner portion including a pair of conductive pillars, and an outer portion including a memory film and a channel film. A method for manufacturing the semiconductor device is also disclosed.

What is claimed is: 
     
         1 . A method for manufacturing a semiconductor device, comprising:
 forming two preformed stack units over a semiconductor substrate, the two preformed stack units being spaced apart from each other by a trench, each of the two preformed stack units including at least one preformed stack and an upper film which is stacked on the at least one preformed stack, and which is made of a dielectric material, the at least one preformed stack including a dielectric film and a sacrificial film which are stacked on each other such that the sacrificial film is disposed between the upper film and the dielectric film;   forming a plurality of separators in the trench, each of the separators bridging the two preformed stack units, two adjacent ones of the separators being spaced apart from each other so as to form a plurality of openings among the separators;   performing a replacement process to replace the sacrificial film of each of the two preformed stack units with a conductive film through the openings; and   after the replacement process, forming a plurality of repeating units in the openings, respectively, each of the repeating units including
 a channel film which is made of a semiconductor material, 
 a memory film which is disposed between the channel film and the conductive film, and 
 a bit line and a source line which are spaced apart from each other, 
   wherein the sacrificial film has an upper surface, a lower surface, and two side surfaces each interconnecting the upper surface and the lower surface, and   wherein before the replacement process, a semiconductor material layer is not formed over each of the upper surface, the lower surface and the two side surfaces of the sacrificial film.   
     
     
         2 . The method of  claim 1 , wherein each of the repeating units is formed by
 forming the memory film and the channel film in a corresponding one of the openings such that the channel film is separated from the conductive film through the memory film, and   forming the bit line and the source line in the corresponding one of the openings such that the bit line and the source line are surrounded by the channel film and separated from each other by an isolation region.   
     
     
         3 . The method of  claim 2 , wherein the bit line and the source line are formed by
 filling an isolation part in the corresponding one of the openings such that the isolation part is surrounded by the channel film,   patterning the isolation part to form two holes which are separated from each other, and   filling a conductive material in the two holes so as to permit the bit line and the source line to be respectively formed in the two holes and so as to permit a remaining region of the isolation part to serve as the isolation region.   
     
     
         4 . The method of  claim 1 , wherein the at least one preformed stack includes a plurality of preformed stacks, a distal one of the preformed stacks having a length shorter than a length of a proximate one of the preformed stacks relative to the semiconductor substrate, the sacrificial films of the preformed stacks being disposed to alternate with the dielectric films of the preformed stacks. 
     
     
         5 . The method of  claim 4 , wherein, in each of the preformed stacks, the sacrificial film and the dielectric film have the same length. 
     
     
         6 . The method of  claim 4 , wherein each of the preformed stack units further includes an inter-metal dielectric (IMD) part formed on the preformed stacks. 
     
     
         7 . The method of  claim 6 , wherein in each of the preformed stack units, an upper surface of the IMD part, which is opposite to the semiconductor substrate, is flush with an upper surface of the upper film. 
     
     
         8 . A method for manufacturing a semiconductor device, comprising:
 forming a stack assembly over a semiconductor substrate, the stack assembly including a plurality of dielectric layers and a plurality of sacrificial layers which are disposed to alternate with the dielectric layers;   patterning the stack assembly such that the patterned stack assembly has a main structure and a staircase structure;   forming an inter-metal dielectric (IMD) layer over the staircase structure;   forming a plurality of trenches in the patterned stack assembly and the IMD layer so as to form a plurality of preformed stack units each including a portion of the IMD layer, a portion of the staircase structure and a portion of the main structure;   forming a plurality of separators in each of the trenches such that each of the separators is disposed to bridge two adjacent ones of the preformed stack units and such that two adjacent ones of the separators are spaced apart from each other to form a plurality of openings among the separators;   performing a replacement process to replace remaining portions of the sacrificial layers with conductive films through the openings, respectively; and   after the replacement process, forming a plurality of repeating units in the openings, respectively, each of the repeating units including
 a channel film which is made of a semiconductor material, 
 a memory film which is disposed to separate the channel film from the conductive films, and 
 a bit line and a source line which are spaced apart from each other, each of the bit line and the source line extending lengthwise along a direction normal to the semiconductor substrate, 
   wherein the sacrificial film has an upper surface, a lower surface, and two side surfaces each interconnecting the upper surface and the lower surface,   wherein, before the replacement process, the memory film is not formed over one of the two side surfaces of the sacrificial film, and   wherein, after the replacement process, and after the memory film of each of the repeating units is formed, the memory film interfaces the conductive film which is positioned in place of the sacrificial film.   
     
     
         9 . The method of  claim 8 , wherein an uppermost one of the dielectric layers is disposed over all of the sacrificial layers. 
     
     
         10 . The method of  claim 9 , wherein
 in the patterned stack assembly, the uppermost one of the dielectric layers is patterned to have a dimension smaller than a dimension of each of the sacrificial layers and a dimension of each of remaining ones of the dielectric layers,   each of the sacrificial layers and the remaining ones of the dielectric layers has a first portion disposed beneath the uppermost one of the dielectric layers, and   the uppermost one of the dielectric layers, the first portions of the sacrificial layers, and the first portions of the remaining ones of the dielectric layers together constitute the main structure of the patterned stack assembly.   
     
     
         11 . The method of  claim 10 , wherein
 in the patterned stack assembly, a distal one of the sacrificial layers has a dimension smaller than a dimension of a proximate one of the sacrificial layers relative to the semiconductor substrate, and a distal one of the dielectric layers has a dimension smaller than a dimension of a proximate one of the dielectric layers relative to the semiconductor substrate,   each of the sacrificial layers and the remaining ones of the dielectric layers has a second portion which extends beyond the uppermost one of the dielectric layers, and   the second portions of the sacrificial layers and the second portions of the remaining ones of the dielectric layers together constitute the staircase structure.   
     
     
         12 . The method of  claim 8 , wherein the dielectric layers are made of a first dielectric material, and the sacrificial layers are made of a second dielectric material different from the first dielectric material. 
     
     
         13 . The method of  claim 8 , wherein each of the repeating units is formed by
 sequentially forming the memory film and the channel film in a corresponding one of the openings,   filling the corresponding one of the openings with an isolation part such that the isolation part is surrounded by the channel film,   patterning the isolation part to form two holes which are separated from each other, and   forming the bit line and the source line in the two holes, respectively, such that the bit line and the source line are separated from each other through a remaining region of the isolation part.   
     
     
         14 . The method of  claim 12 , wherein each of the separators is made of a third dielectric material which is different from each of the first dielectric material and the second dielectric material. 
     
     
         15 . A method for manufacturing a semiconductor device, comprising:
 forming a first preformed stack unit and a second preformed stack unit over a semiconductor substrate, the first preformed stack unit and the second preformed stack unit being spaced apart from each other by a first trench, each of the first preformed stack unit and the second preformed stack unit including a sacrificial film and a dielectric film which are stacked on each other and which are respectively made of a first material and a second material, the first material being different from the second material;   forming a plurality of first separators in the first trench, each of the first separators bridging the first preformed stack unit and the second preformed stack unit, two adjacent ones of the first separators being spaced apart from each other so as to form a plurality of first openings among the first separators, each of the first separators being made of a third material that is different from each of the first material and the second material;   after formation of the first separators, performing a replacement process through the first openings to replace the sacrificial film of the first preformed stack unit with a first conductive film and to replace the sacrificial film of the second preformed stack unit with a second conductive film; and   after the replacement process, forming a plurality of first repeating units respectively in the first openings, each of the first repeating units including
 a first channel film which is made of a semiconductor material, 
 a first memory film which is disposed to separate the first channel film from each of the first conductive film and the second conductive film, and 
 two first conductive pillars which are separated from each other by an isolation region and which respectively serve as a bit line and a source line, 
   wherein the sacrificial film has an upper surface, a lower surface, and two side surfaces each interconnecting the upper surface and the lower surface, and   wherein, before the replacement process, each of the two first conductive pillars and the first memory film is not formed over one of the upper surface, the lower surface and the two side surfaces of the sacrificial film.   
     
     
         16 . The method of  claim 15 , wherein
 each of the first repeating units including
 a first inner portion which includes the two first conductive pillars that are separated from each other, and 
 a first outer portion which surrounds the first inner portion so as to separate the first inner portion from each of the first conductive film, the second conductive film and two adjacent ones of the first separators, the first outer portion including the first memory film and the first channel film which is disposed between the first memory film and the first inner portion. 
   
     
     
         17 . The method of  claim 15 , further comprising:
 forming a third preformed stack unit over the semiconductor substrate, the second preformed stack unit and the third preformed stack unit being spaced apart from each other by a second trench, the third performed stack unit including a sacrificial film and a dielectric film which are stacked on each other, and which are respectively made of the first material and the second material;   forming a plurality of second separators in the second trench, each of the second separators bridging the second preformed stack unit and the third preformed stack unit, two adjacent ones of the second separators being spaced apart from each other so as to form a plurality of second openings among the second separators, each of the second separators being made of the third material, the second separators being staggered from the first separators, respectively;   replacing the sacrificial film of the third preformed stack unit with a third conductive film through the second openings; and   forming a plurality of second repeating units respectively in the second openings.   
     
     
         18 . The method of  claim 15 , further comprising:
 forming a third preformed stack unit over the semiconductor substrate, the second preformed stack unit and the third preformed stack unit being spaced apart from each other by a second trench, the third performed stack unit including a sacrificial film and a dielectric film which are stacked on each other, and which are respectively made of the first material and the second material;   forming a plurality of second separators in the second trench, each of the second separators bridging the second preformed stack unit and the third preformed stack unit, two adjacent ones of the second separators being spaced apart from each other so as to form a plurality of second openings among the second separators, each of the second separators being made of the third material, the second separators being in alignment with the first separators, respectively;   replacing the sacrificial film of the third preformed stack unit with a third conductive film through the second openings; and   forming a plurality of second repeating units respectively in the second openings.   
     
     
         19 . The method of  claim 18 , wherein
 each of the second repeating units including
 a second inner portion which includes two second conductive pillars that are separated from each other, and 
 a second outer portion which surrounds the second inner portion so as to separate the second inner portion from each of the second conductive film, the third conductive film and two adjacent ones of the second separators, the second outer portion including a second memory film and a second channel film which is disposed between the second memory film and the second inner portion, and 
 the two first conductive pillars of each of the first repeating units are in alignment with the two second conductive pillars of each of the second repeating units, respectively. 
   
     
     
         20 . The method of  claim 18 , wherein the sacrificial film of the third preformed stack unit is replaced with the third conductive film before formation of the second repeating units.